Ion implantation is a physical process, as opposed to diffusion, which is a chemical process that is employed in semiconductor apparatus fabrication to selectively implant dopant into a semiconductor workpiece and/or wafer material. Thus, the act of implanting does not rely on a chemical interaction between a dopant and the semiconductor material. For ion implantation, dopant atoms/molecules are ionized and isolated, sometimes accelerated or decelerated, formed into a beam, and swept across a workpiece or wafer. The dopant ions physically bombard the workpiece, enter the surface and typically come to rest below the workpiece surface in the crystalline lattice structure thereof.
In RF based accelerators, ions are repeatedly accelerated through multiple RF voltage driven acceleration gaps. Due to the time varying nature of RF acceleration fields and the multiple numbers of acceleration gaps (usually greater than 20) there are a large number of parameters which influence the final beam energy. Although it may not be technically impossible, “set and forget” techniques can not be used in setting up the final beam energy and fine adjustments have to be performed on the parameters to maximize beam transmission through a filter with known passband.
An energy filter is used not only as a simple filter to reject unwanted portions of the energy spectrum, but also and more importantly as an energy standard to which all the acceleration parameters are tuned. In this sense, the energy filter plays the ultimate role in determining the final beam energy. However, quite often the design of the energy filter has to be compromised, mostly because of space restrictions or some other imposed conditions limiting proper functioning and as a result, precision in the final beam energy is uncertain. There have been several attempts to develop an independent measurement system of beam energy, but no particular method has been incorporated into production machines.
Accordingly, suitable systems or methods for identifying beam energy are desired, that accurately measures the final beam energy.